The present invention relates generally to counter-balance mechanisms for automatically controlling the opening or closing movement of sashes, doors or other closure members on housings or enclosures. More particularly, the invention relates to such counterbalance mechanisms that are especially well-suited for use in fume hoods, laboratory station enclosures, work chambers or other such housings or enclosures having systems for ventilating or exhausting their interiors.
Laboratory fume hoods and other such work station enclosures generally include a housing or other enclosed interior having an opening providing the user with access for performing various operations within an interior work chamber. Typically, a sash, door or other closure member is movably disposed within the access opening for opening or closing the enclosure. Because the operations conducted in such interiors often involve undesirable gases, fumes or vapors, these enclosures frequently include an exhaust conduit communicating the interior work space with a blower or other gas conveying device for removing such gases, fumes or vapors and for substantially preventing their escape into the surrounding environment.
In addition to the above components, these fume hoods or work enclosures typically include one or more counterweights that counterbalance the weight of the sash and any other forces tending to close the sash or door, thus allowing it to stay in a selected position when released by the operator. These counterbalance systems can include spring members that counterbalance the weight of the sash and can include sash weights hidden within the frame of the fume hood and cables that extend over pulleys and interconnect the sash or other closure member with the counterweights.
In many laboratories or other such facilities, fume hood enclosures are required to be large in order to allow relatively large equipment to be freely inserted into the interior work chamber. However, these configurations have resulted in unduly expensive exhaust equipment and high operating costs needed for exhausting the interior work chamber and maintaining it at a lower pressure than that of the surrounding environment due to the large access openings. These expenses have also been aggravated by the operating costs associated with replacing and reconditioning relatively large amounts of conditioned air from the surrounding environment that was lost by way of the large fume hood access opening and the exhaust system. In addition, although most users typically open fume hood sashes only enough to provide adequate access for performing the desired operations, these closure members are sometimes inadvertently left fully open or near fully open, in an at-rest position, after the user has completed the operations and vacated the area, thus further contributing to such increased expenses and costs.
In order to eliminate or substantially minimize these problems, a number of prior art devices have been proposed for automatically returning sashes or other closure members to either closed or minimally open positions. These solutions, however, have often involved tandem or multiple counterweight arrangements, and sensor-activated motorized closing equipment, for example, and thus have proved to be too complex, expensive or otherwise disadvantageous to be either effective or cost-justified in many fume hood or work chamber applications.
One such prior art device is disclosed in Schiles U.S. Pat. No. 5,688,168. In this patent the counterweight system includes a primary counterweight and a second adjusting weight. The second adjusting weight is arranged to add to the weight of this primary counterweight during certain movement of the sash to thereby allow the sash member to drop to a predetermined position after it is raised above that point. The second adjusting weight is dropped off of the primary counterweight during other movement of the sash.
One major disadvantage of this system is that the adjusting weight and the primary counterweight are both static, and the weight adjustment can be made at only one finish point during the vertical movement of the sash.
The present invention seeks to overcome these and other disadvantages and to further improve on prior art devices.
All embodiments of the present invention include an enclosure having an interior chamber, an access opening in the enclosure providing access to the interior chamber, a closure member movable between closed and fully open positions in the access opening for selectively allowing and restricting access to the interior chamber. The present invention relates to improvements in the counterweight system used with the closure member.
One series of embodiments of the present invention relate to an apparatus and method for uniquely using force moments to vary the effective weight of the counterweight and control the movement of a closure member, such as the sash of a fume hood. The first of these embodiments includes at least one primary counterweight, a primary connecting member interconnecting the primary counterweight and the closure member for movement therewith, and a primary roller member mounted for rotation about an axis of rotation, the primary roller member being engaged by the primary connecting member intermediate the primary counterweight and the closure member for rotation by the primary connecting member in response to movement of the closure member. Additionally, this embodiment includes at least one secondary counterweight, a secondary roller member arranged to rotate with the first roller member, and a secondary connecting member interconnecting the secondary roller member and the secondary counterweight, the secondary member movably winding and unwinding on the secondary roller member in response to movement of the closure member. When the closure member is moved between its fully closed position and a predetermined intermediate position between the closed and fully open positions, the secondary connecting member winds and unwinds from the secondary roller member in a first moment-producing direction on the secondary roller member. When the closure member is moved between the its fully opened position and the intermediate position, the secondary connecting member winds and unwinds on the secondary roller member in a second moment-producing direction on the secondary roller member, the second moment producing direction being opposite to the aforesaid first moment-producing direction.
Preferably, the closure member is a sash member movable generally vertically between the fully closed and fully open positions, and the primary and secondary counterweights maintain the closure member in a substantial stationary at-rest condition when the closure member is located at its predetermined intermediate position between its fully open and fully closed positions. The connecting members may be a chain or toothed belt engaging the outer periphery of teeth formed on pulleys, or a cable having one end fixedly interconnected to a pulley, or a cable having a traction-surface thereon for positively engaging a pulley. The primary and secondary pulleys may have diameters which are the same or different from one another.
The primary counterweight may be a single u-shaped weight, or a plurality of weights, each connected to the closure member by a separate connecting member, and some or all of the rollers may be pulleys that are connected together by a shaft for rotation about the axis of rotation of the shaft. The secondary counterweight may be attached to the shaft at a position intermediate the point at which two primary counterweights engage the shaft. Alternatively, the primary and secondary pulleys may be joined integrally as a double-grooved pulley mounted for rotation about an axis of rotation.
In another embodiment of the present invention generally similar the first embodiment described above, at least one primary counterweight is used as in the first embodiment described above. This embodiment also includes a pair of secondary counterweights, a respective pair of secondary roller members rotatably fixed relative to the primary roller member for rotation therewith, and a pair of respective secondary connecting members each having an end portion fixedly interconnected with a respective one of the secondary roller members and an opposite end portion fixedly interconnected with a respective one of the secondary counterweights. The secondary connecting members wind and unwind on the secondary roller members in response to movement of the closure member. In this embodiment, the closure member is movable to first and second predetermined intermediate positions between the fully closed and fully open positions, with each of the secondary members movably unwinding in a first moment-producing direction on one of the respective secondary roller members, when the closure member is moved between its fully closed position and the first intermediate position. One of the secondary connecting members winds and unwinds in the first moment-producing direction on one of the respective secondary roller members and the other of the secondary connecting members winds and unwinds in a, second opposite moment-producing direction on the other of the respective secondary roller members when the closure member is moved between the first intermediate position and the second intermediate position. Both of the secondary connecting members wind and unwind in the second moment-producing direction on the respective secondary roller members when the closure member is moved between the second intermediate position and the fully open position. Preferably, the secondary counterweights produce respective opening moments assisting the opening movement of the closure member when the respective secondary connecting members wrap and unwrap on the respective secondary roller members in the first moment-produce direction, and produce second respective closing moments assisting the closing movement of the closure member when the respective secondary connecting members wrap and unwrap on the respective secondary roller members in the second opposite moment-producing direction. It is also preferable that the primary and secondary counterweights maintain the closure member in a substantial stationary at-rest condition when the closure member is at a first predetermined intermediate position between the fully closed position and the fully open position.
Another series of embodiments of the present invention include an apparatus and method of utilizing a unique arrangement for varying the effective weight of the counterweight using vectoring of the forces applied by the counterweight to control the movement of the closure member. One of these embodiments includes at least one counterweight, at least two connecting members, each interconnecting the counterweight and the closure member, and at least two guide members disposed between the counterweight and the closure member. The two connecting members extend over the two guide members, respectively, so that the counterweight and the closure member move together in opposite vertical directions, with the two guide members being positioned so that the portions of the two connecting members extending between the support members and the closure member extend at an angle to vertical that varies as the closure member moves between the closed and fully open position to thereby vary the effective vertical counterweight forces exerted on the closure member by the counterweight. Preferably, the two guide members are rollers spaced from one another, and the closure member moves in a vertical path of movement that is between the rollers. It is also preferred that the effective vertical counterweight force is equal to the weight of the closure member when the closure member is moved to a predetermined intermediate position between the fully open and fully closed position of the closure member.
Another embodiment of the present invention includes a counterweight, and a connecting member connecting the counterweight to the closure member. At least one guide member is disposed between the counterweight and the closure member with the connecting member extending over the guide member so that the counterweight and the closure member can move together in opposite vertical directions. A track member is disposed in the path of the vertical movement of the counterweight and extends at an angle to the vertical path of movement of the counterweight whereby the counterweight will engage the track member during a predetermined portion of its downward movement and will be moved at an angle away from the vertical path of movement to thereby vary the effective vertical counterweight force exerted on the closure member by the counterweight. Preferably, a rotatable engagement member, such as a roller, is mounted on the counterweight and positioned to rotatably engage the track member. The portion of the connecting member extending between the guide member and the counterweight extends in a vertical direction during movement of the counterweight when it is not in engagement with the track member, and extends at an angle to vertical when the counterweight is in engagement with the track member, such angle increasing as the counterweight moves downwardly along the track member. It is also preferable that two guide members and two connecting members be provided, with the guide members located vertically above the counterweight so that the portions of the connecting members extending between the guide members and the counterweight will extend in a vertical direction during movement of the counterweight when it is not in engagement with the track member and will extend at an angle to vertical when the counterweight is in engagement with the track member, this angle increasing as the counterweight moves downwardly along the track member.
In yet another embodiment of the present invention, a counterweight is provided, and a first connecting member connects the counterweight to the closure member. At least one guide member is disposed between the counterweight and the closure member with the first connecting member extending over the guide member so that the counterweight and the closure member can move together in opposite vertical directions. A second connecting member extends between the counterweight and a fixed element in the enclosure, the second connecting member having a fixed length. The fixed element is located to cause the second connecting member to move the counterweight at an angle away from the vertical direction of movement to thereby vary the effective vertical counterweight force exerted on the closure member by the counterweight. Preferably, the effective vertical counterweight force is varied to result in such force being less than the weight of the closure member when the closure member moves between the fully open position and a predetermined intermediate position between the fully closed and fully open positions, and to result in the such force being substantially equal to the weight of the closure member when it is at the predetermined intermediate position.
In another embodiment of the present invention, at least one counterweight is provided, and a pulley is located between the counterweight and the closure member. The pulley is formed with two sides that extend radially outwardly along gradually diverging extents to form a groove therebetween that gradually increases from the inner edge of the groove to the outermost edge of the pulley. A connecting member interconnects the closure member and the counterweight and is disposed in the groove of the pulley, and the connecting member is formed with a first segment having a first predetermined width joined to a second segment having a second predetermined width that is less that the first predetermined width, whereby the effective weight of the counterweight as applied to the weight of the closure member is varied depending on which of first or second segments are disposed in the groove of the pulley. Preferably, the first segment of the connecting member is joined to the second segment of the connecting member by an intermediate transition segment, and the intermediate transition segment is disposed within the groove of the pulley when the closure member is located at its predetermined intermediate position between its fully opened and fully closed positions.
Additional objects, advantages and features of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings.